Vibratory element and method of producing the same



H. F. FRUTH June 24, 1930.

VIBRATORY ELEMENT ANDMETHOD OF PRODUCING THE SAME Filed Dec. 31, 1928 Patented June 24, 1930 UNITED STATES PATENT ori-*ICE HAL FREDERICK FRUTH, OF CHICAGO, ILLINOIS, ASSIG-NOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, .0F NEW YORK, N. Y., A CORPORATION OF NEW YORK VIBRATORY ELEMENT AND vMIEITHOD OF PRODUCING THE SAME Application filed December rlhis invention relates to vibratory ele-.-

ments and methods of producing the same, and more particularly to diaphragms intended for use in microphones and telephone transmitters. u

. An object of this invention is to provide an improved method for applying to a diaphragm an electrode consisting of a thin metallic coating of even thickness which shall thoroughly adhere thereto without any tendency to separate therefrom.

To accomplish the above and other 0bjects, an electrode is applied to a diaphragm in the form of a thin coa ing by a cathodic sputtering process, wher by the coating is so hammered into the metal of the dia-` phragm that it is extremely adherent at all points and does not tend to separate therefronusince no electrolytic action takes place Fig. 2 is an enlarged perspective view of` a vibratory element formed in accordance with the invention.

In the drawings,'which-illustrate a preferred form of the invention without limiting it, the reference numeral 10 designates a base uponwhich is supported a bell'jar or other suitable vacuum chamber forming means 11. An Iexhaust tube 12 4leads from the vacuum chamber to a vacuum pump (not shown) and is provided with an arm 13 in which is mounted an anode 14.

A plurality of cathodes 16, preferably consisting of anoble metal, such as gold, platinum, etc., to be deposited on the diaphragms, are supported in the vacuum chamber in spaced relation by means of an insulating member 17 having arms 18fterminating in conical shields 20'which overlie the cathodes. The cathodes are connected tov anode 14 by means of. an electric circuit 21 which includes the secondary of' 31,1328. serial No. 329,646.

` 'a transformer 22. While only two cathodes are shown in the drawings, it will be understood that any desired number may be used within the limits of the space available within the vacuum chamber.

`Within the vacuum chamber is positioned a support Qilfor the diaphragms 25 to which the electrodes are to be applied, and plates 26, which may be of fiat annular form, protect those parts of the diaphragm to which the coating is not. to be applied. The pressure within` the vacuum chamber -is indicated by a gauge 28 and may be controlled by a manually operated bleeder valve 29. It will be understood that when a suitable vacuum, 'corresponding to .l mm. of mercury 'or thereabouts, is produced in the chamber, and the transformer 22 is energized, current will flow therefrom to cathodes 16 and thence through the exhausted atmosphere to anode 14 in the known manner, carrying with it particles of the metal forming the cathodes 16 and depositing such particles upon any objects which may lie in their path, thus coating the exposed .or central portion 27V of the diaphragme. In order to prevent reversal of this action, the total surface area of cathodes 16 is made several times greater than that of anode 14, although the same result may be obtained by inserting a rectifier' in the circuit 21. The coating process continues for such time asis found by experience to be necessary `to produce an electrode of the desired thickness,whereupon the diaphragme are inverted and electrodes apoplied to their opposite faces, provided that oth faces are to have electrodes thereon.

Diaphragms having electrodes secured thereto in accordance with this invention have excellent mechanical and acoustic properties, and their useful life is increased Without departing from the spirit of the invention as defined in the following claims. i What is claimed is:

l. The method of applying a metallic microphonic electrode member to another member which consists in depositing thereon by cathodic sputtering a coating of the metal to form the metallic member.

2. The method of applying a metal electrode to a telephone diaphragm which con`- sists in exposing a portion of the diaphragm to the action of metal-carrying cathode rays.

3. The method of producing a vibratory element which consists in oathodically sputtering a noble metal upon a predetermined portion of a diaphragm to form an electrode thereon.

4. A vibratory element consisting of a diaphragm having an electrode produced thereon by cathodic sputtering- 5. A vibrator# lement for use in microphones and telephone transmitters, consisting of a diaphragm having on at least one of its faces a noble metal electrode deposited by cathodic sputtering.

6. A vibratory element consisting of a base metal diaphragm having-on one of its faces a noble metal electrode deposited by cathodic sputtering.

7. A vibratory element consistingU of a metal diaphragm having on at least one of its faces a gold electrode deposited by eathodic sputtering. l

In Witness whereof, I hereunto subscribe my name this 19th day of December, A. D.

HAL FREDERICK FRUTH. 

